The present invention relates to a thermosetting resin forming composition. The composition has good storage stability and provides the resulting thermosetting resin with excellent mechanical strength and low water absorption, without impairing heat resistance.
Thermosetting resins having an imide structure have traditionally provided excellent performance properties such as electrical insulation, heat resistance and dimensional stability of molded articles. Therefore, they have been widely utilized in many industrial fields.
However, although thermosetting resin forming compositions obtained by thermally polymerizing only an aromatic base bismaleimide compound have provided materials which exhibit excellent heat stability, they unfortunately have a disadvantage of exhibiting extreme brittleness and poor flexibility.
One method for addressing this disadvantage relates to the use of a thermosetting resin forming composition composed of an aromatic base bismaleimide compound and an aromatic base diamine compound. For example, a polyaminobismaleimide resin composed of N,N'-4,4'-disphenylmethanebismaleimide and 4,4'-diaminodiphenylmethane (Trade Mark; Kelimide, a product from Rhone Poulenc Co.) has been widely used commercially as an impregnating varnish, a laminated sheet and a molded article as described in Japanese Patent Publication No. 23250 (1971). The above thermosetting resin forming composition, however, does not provide satisfactory impact resistance and flexibility.
Furthermore, when such a thermosetting resin forming composition is used as a base material of electrical and electronic parts, the resulting parts exhibit high water absorption which adversely effects processability and electrical properties.
Also, when such a thermosetting resin forming composition is used for laminated sheets, the composition exhibits poor solubility in low boiling point solvents and inferior storage stability of the resin solution prior to preparation of the prepreg of glass cloth.